Guanidyl Paper Coating

ABSTRACT

Herein is described a coating composition for the production of paper, for example, for use in inkjet printing. The coating composition includes a guanidyl dye fixative and optionally a binder and/or a filler. The paper product includes a paper substrate, and a coating layer carried by the paper substrate that includes a guanidyl dye fixative. The manufacture of the coated paper is provided by a process that includes applying the coating composition, which includes the guanidyl dye fixative, to paper.

CROSS-REFERENCE TO RELATED APPLICATIONS

This disclosure claims the benefit of priority to U.S. Provisional Patent Application No. 62/087,963, filed Dec. 5, 2014, the disclosure of which is incorporated herein in its entirety.

FIELD OF THE INVENTION

This disclosure is directed to compositions and methods of surface coating fibrous material for the production of a coated paper. The compositions and methods include a guanidyl dye fixative.

BACKGROUND

Current trends in color printing and development of fast inkjet printers have created an increased need for coated inkjet papers. High end inkjet coatings were originally based on silica fillers, a polyvinyl alcohol binder (PVA), and a group 2-13 cation additive (e.g., calcium salts). This media provided excellent print quality by enabling rapid and efficient fixation of the anionic inkjet colorants to the coating. However, the expense of the silica grades, slow coating methods (caused by low viscosity of coating mixtures), and the considerable need for binders limited more widespread use.

Coating components typically used for conventional printing papers are not applicable to inkjet printing, because of their low affinity to anionic inkjet dyes and inadequate absorption capacity. Thus, improvements in inkjet print quality required modification of the filler or polymer composition used in conventional coatings. Several approaches are represented in the art, including the use of ground or precipitated calcium carbonate, kaolin, bentonite, and/or surface enhanced aluminosilicate (SEAS).

SUMMARY

A first embodiment is a coating composition, the composition including a binder and/or a filler, and a guanidyl dye fixative.

A second embodiment is a coated paper which includes a paper substrate and a coating layer carried by the paper substrate; the coating layer comprising a guanidyl dye fixative.

A third embodiment is a process of forming the coated paper. The process includes applying the coating composition, which includes a guanidyl dye fixative, to paper, and then drying the composition to provide the coated paper that has a coating layer carried by the paper.

DETAILED DESCRIPTION

Disclosed herein are coating compositions for the manufacture of paper (e.g., for use in inkjet printing), compositions and structures of coated paper manufactured with the coating compositions, and means for manufacturing the coated paper. Whereas common coating compositions employ anionic dye fixatives, the coating compositions disclosed herein include a guanidyl dye fixative.

Herein, the term coating composition refers to the liquid compositions used to provide a coating layer, for example, on paper. The coating composition can be, for example, a sizing composition. Preferably, the coating composition is applied to a substrate, for example, a woven or non-woven substrate. Preferably, the substrate is a non-woven substrate that includes plant fibers. More preferably, the substrate is paper.

The terms precipitate and flocculate have or imply the same action, the formation of a solid or heterogeneous material that separates, is separable, or affects the rheology of the supporting solution. As used herein, the terms, precipitate/flocculate, can be used interchangeable unless the mechanism of formation or separation is specified in detail.

As provided herein, the coating composition includes a guanidyl dye fixative. In one instance, the coating composition further includes a filler. In another instance, the coating composition further includes a binder. In a preferable embodiment, the coating composition is carried on a paper substrate. In another example, a coated paper (e.g., for use in inkjet printing) includes a paper substrate and a coating layer carried by the paper substrate that comprises a guanidyl dye fixative and, optionally, a binder and/or a filler. In another example, the coated paper carries on a surface a coating layer (e.g., a dried coating composition) that includes the guanidyl dye fixative and, optionally, a binder and/or a filler. As used herein, the coating composition is, preferably, a liquid material that is useful for applying to paper; the coating composition can be carried by paper (for example, by wetting the paper or a paper surface with the coating composition); and the coating layer is a dry composition carried directly by the paper and made by the removal of solvent from the coating composition carried by the paper.

In one instance, the coating composition, alone or carried on the paper, includes a filler. The filler can be selected from one of, a set/selection of, or a mixture of calcium carbonate, a kaolinite, a silicate, an aluminate, an aluminosilicate, a titanate (e.g., TiO₂), and a zincate (e.g., ZnO₂, CaZrO₃). Preferably, the filler is selected from a calcium carbonate, a kaolinite (kaolin), or a mixture thereof. In one instance, the filler is a calcium carbonate; in another instance, the filler is a kaolinite. Examples of a kaolinite include kaolin, metakaolin, calcined kaolin, or a mixture thereof. Notably, the coating composition and the coating layer carried on the paper substrate can differ significantly in the weight percentages of the materials included in the compositions; these differences can be associated with the presence or absences of a carrying solvent (e.g., water). In a coating composition that is intended to be applied to a paper substrate, the composition preferably includes a solvent (e.g., water). In a coating layer carried by the paper substrate, the composition is preferably dried and does not include the same amount of the solvent as the solution based composition. Notably, the inclusion of the solvent in the composition can have significant effects on the reported weight percentage of the materials in the coating composition. As used throughout, the reported compositions are determined based on the dry weight; that is, the weight percentages of the included materials without the solvent(s). In instances where the coating composition or the coating layer includes the filler, the composition can include about 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, or 85 wt. % of the filler. In another instance, the composition can include about 20 wt. % to about 80 wt. %, about 30 wt. % to about 75 wt. %, about 40 wt. % to about 70 wt. %, about 45 wt. % to about 65 wt. %, or about 50 wt. % to about 60 wt. % of the filler.

In another instance, the coating composition, alone or carried on the paper includes a binder. The binder is, preferably, a polymeric material used, for example, to bind the filler to the paper. Binders can be selected, for example, to improve the water retention and rheology of the coating composition. In one example, the binder can be one of, a set/selection of, or a mixture of a styrene butadiene copolymer, a styrene acrylate copolymer, dextrin, an acrylic/vinyl acetate polymer, a starch (e.g., a cationic and/or an ethylated starch), guar gum, a guar (e.g., a cationic guar), a cellulose (e.g., a methyl cellulose, an ethyl cellulose, a hydroxyethyl cellulose, and/or a carboxymethyl cellulose), a polyvinyl alcohol, a polyvinylacetate, a latex, an acrylic polymer, an acrylic copolymer, a styrene-acrylate copolymer, a polyethylene-polyvinyl acetate, a polyethylene-polyvinylalcohol, and sodium alginate. In one aspect, the composition can include about 0.1 wt. %, 0.2 wt. %, 0.5 wt. %, 1 wt. %, 5 wt. %, 10 wt. %, 15 wt. %, 20 wt. %, 25 wt. %, 30 wt. %, 35 wt. %, 40 wt. %, 45 wt. %, or 50 wt. % of the binder (dry basis); in another aspect that composition can include at least about 5 wt. %, 10 wt. %, 20 wt. %, 30 wt. %, or 40 wt. % of the binder. In another instance, the composition can include about 1 wt. % to about 50 wt. %, about 2 wt. % to about 45 wt. %, or about 3 wt. % to about 40 wt. % of the binder.

The coating composition and/or coating layer can further include a surfactant. Preferably, the composition can include about 0.1 wt. %, 0.2 wt. %, 0.5 wt. %, 1 wt. %, 5 wt. %, 10 wt. %, 15 wt. %, 20 wt. %, 25 wt. %, 30 wt. %, 35 wt. %, 40 wt. %, 45 wt. %, or 50 wt. % of the surfactant. It is common to characterize surfactants by a hydrophile-lipophile balance value, also known as HLB value. Surfactants with a low HLB are more lipid loving and thus tend to make a water in oil emulsion while those with a high HLB are more hydrophilic and tend to make an oil in water emulsion. When combinations of surfactants are used, the weighted average of the individual surfactant components is used to calculate the HLB of the combination. The preferred surfactant combination for the emulsion has an HLB value of about 6 to about 25. More preferred is an HLB of 8 to 20. Yet more preferred is an HLB of 9 to 18. And even more preferred is an HLB of from 11 to 16.

Surfactants that are useful in the present invention include, without limitation, ethoxylated alcohols, ethoxylated carbohydrates, ethoxylated vegetable oils, polyethyleneglycols (PEG), polypropylene glycols (PPG), monoesters and diesters of PEG and PPG, ethoxylated amines, fatty acids, ethoxylated fatty acids, fatty amides, fatty diethanolamides, and the like. Examples of specific surfactants, and commercial sources, include oleyl alcohol 10 EO (Ethox Chemical), Tween 20 (Uniqema), stearyl alcohol 20 EO (Ethox Chemical), castor oil 80 EO (Ethox Chemical), castor oil 30 EO (Ethox Chemical), PEG 400 Dioleate (Ethox Chemical), tallow amine 5 EO (Akzo Nobel), Burco TME-S (Burlington Chemical), coconut diethanolamide (Ethox Chemical), Ethfac 161 (Ethox Chemical), cocoamine 2 EO (Akzo Nobel), cocoamine 5 EO (Akzo Nobel), Dowanol DB (Dow Chemical), Demulse DLN 532 CE (Deforest Enterprises), Tween 80 (Uniqema), Demulse DLN 622 EG (Deforest Enterprises), Span 20 (Uniqema), Diacid 1550 (Westvaco), decyl alcohol 4 EO (Ethox Chemical), dipropyleneglycol methyl ester (Dow Chemical), sodium lauryl sulfate (SLS), sodium dodecyl sulfate (SDS), sodium xylenesulfonate (SXS), and Tergitol NP6 (Dow Chemical).

Preferably, the guanidyl dye fixative is a guanidyl copolymer that can be prepared, for example, from the condensation polymerization of a guanidyl reactant and a carbonyl reactant, see for example, U.S. Pat. No. 5,659,011, incorporated herein by reference in its entirety. In another embodiment, the guanidyl copolymer can be prepared from the condensation polymerization of a guanidyl reactant and an imine reactant. Typically, a condensation reaction is an acid or base catalyzed polymerization that produce(s) water, an alcohol, and/or an amine as a by-product.

In one instance, the guanidyl copolymer is a cationic guanidyl copolymer, and, preferably, maintains a level of cationicity up to a pH of about 9, about 10, about 11, or about 12. In one embodiment, the cationicity of the polymer, as measured in milliequivalents per gram, varies by less than about 75%, more preferably less than about 50% from a pH of about 3 to a pH of about 10.

In another instance the guanidyl copolymer is amphoteric guanidyl copolymer (see alkaline-catalyzed guanidyl copolymer below). Unlike cationic guanidyl copolymers which exhibit constant levels of cationicity over broad pH ranges, the herein described amphoteric dye fixative can have an isoelectric point (pi) in the range of about 3 to about 11, about 4 to about 10, about 5 to about 9, about 5 to about 8, about 5 to about 7, about 5 to about 6, about 6 to about 9, about 7 to about 9, or about 8 to about 9.

The guanidyl copolymer can have a weight average molecular weight in a range of about 1,000 Dalton (D) to about 1,000,000 D; about 1,000 D to about 100,000 D; about 1,000 D to about 75,000 D; about 1,000 D to about 50,000 D; about 1,000 D to about 25,000 D; about 2,000 D to about 25,000 D; about 3,000 D to about 25,000 D; about 4,000 to about 25,000 D; or about 5,000 D to about 25,000 D. Preferably, the weight average molecular weight is in the range of about 1,000 D to about 30,000 D, more preferably about 1,000 D to about 20,000 D. The guanidyl copolymer can further have a degree of branching of about 10 to about 90%.

The guanidyl copolymer can be made by the condensation of an amine reactant selected from dicyanodiamine, guanamine, guanidine, melamine, cyanamine, guanylurea, or a mixture thereof; and/or a carbonyl reactant selected from formaldehyde, paraformaldehyde, urea, thiourea, glyoxal, acetaldehyde, propionaldehyde, butrylaldehyde, glutaraldehyde, acetone, or a mixture thereof.

The guanidyl copolymer can be made, for example, from about 1 wt. % to about 95 wt. %, about 10 wt. % to about 40 wt. %, or 10 wt. % to 40 wt. % guanidyl reactant; about 0 wt. % to about 95 wt. %, about 10 wt. % to about 40 wt. %, or 10 wt. % to 40 wt. % functional amine reactant; about 1 wt. % to about 98 wt. %, about 10 wt. % to about 40 wt. %, or 10 wt. % to 40 wt. % water-soluble salt; and about 1 wt. % to about 98 wt. %, about 10 wt. % to about 40 wt. %, or 10 wt. % to 40 wt. % carbonyl or imine reactant.

In a particular embodiment, the cationic guanidyl copolymer is the condensation product of an amino base, formaldehyde, an alkylenepolyamine, and an inorganic or organic acid (e.g., HCl, H₂SO₄, H₃PO₄, formic acid, acetic acid, citric acid, glycolic acid, boric acid, HF, NH₄Cl). Condensates of this type are described in U.S. Pat. Nos. 3,106,541, 3,410,649, 3,582,461, and 4,383,077, the disclosures of which are incorporated herein by reference. In another embodiment, the amphoteric guanidyl copolymer is the condensation product of an amino base, formaldehyde, an alkylenepolyamine, and an alkali metal or ammonium salt (e.g., ammonia salts of the above organic acids (e.g., formic acid, acetic acid, citric acid, glycolic acid) and/or the inorganic acids (e.g., HCl, H₂SO₄, H₃PO₄, boric acid, HF) in the form of, for example, NH₄ formate, NH₄ acetate, NH₄ sulfate, NH₄ sulfite, NH₄ pyruvate, [NH₄]₃[PO₄], NH₄ citrate, NaOH, and NH₄OH), made at a neutral or alkaline pH (for example, pH 8-10). Condensates of this type are described in U.S. Pat. No. 3,015,649 which is incorporated herein by reference. Notably and as used herein, the cationic and amphoteric guanidyl copolymers are, respectfully, an acid-catalyzed guanidyl copolymer and an alkaline-catalyzed guanidyl copolymer.

The guanidyl reactant can be selected from a group consisting of guanidine, guanidine salts, cyanamide, dicyanamide, biguanide, guanylurea, guanylthiourea, polycyclic guanidine, N-(4-aminobutyl)guanidine, 2-amino-5-guanidinopentanoic acid, imidodicarbonimidic diamide, (N-butylimidocarbonimidic diamide), (2-(methylguanidino) ethanoic acid), (2-[carbamimidoyl(methyl)amino]ethyl dihydrogen phosphate), cyanoguanidine, (2-guanidinoacetic acid), (3-(diaminomethylideneamino)propanoic acid), (N,N-dimethylimidodicarbonimidic diamide), (1-nitroguanidine), (4-amino-N-[amino(imino)methyl]benzenesulfonamide), (2-[10-(diaminomethylideneamino)decyl]guanidine dihydrochloride), melamine, alkyl guanidine, aryl guanidine, alkylaryl guanidine, alkyl biguanide, aryl biguanide, alkylaryl biguanide and combinations, salts, derivatives thereof and mixtures thereof. In another embodiment, the guanidyl reactant can be selected from the group consisting of guanidine, 2-cyanoguanidine, and a mixture thereof. In still another embodiment, the guanidyl reactant can be selected from the group consisting of guanidine, guanidine salts, biguanide, cyanoguanidine, melamine, and a mixture thereof.

The carbonyl reactant can be selected from a group of compounds that have a carbonyl functional group, for example, an aldehyde, a ketone, a urea, an amide, and a mixture thereof. Examples of carbonyl reactants include formaldehyde, acetaldehyde, paraformaldehyde, trioxane, urea, thiourea, glyoxal, acetaldehyde, propionaldehyde, butrylaldehyde, glutaraldehyde, acetone, and/or a formaldehyde source material (e.g., hexamethylenetetramine). The carbonyl reactant can further include protected aldehydes, e.g., acetals. The imine reactant, for example, can be an aldimine, ketimine, imidate, amidate, or a mixture thereof.

The guanidyl copolymer can further include a functional amine reactant. Herein, a functional amine reactant can be an alkylenepolyamine having the formula (alkyl)_(x)(amine)_(y) where the alkyl is selected from the group consisting of ethyl, propyl, butyl, pentyl, hexyl, and a mixture thereof, where x is in a range from 1 to 10, and y is in a range of 2 to 11; an aminoethylpiperizine; an alkanolamine; and a mixture thereof. For example, the alkylenepolyamine can be ethylenediamine, diethylenetriamine, triethylenetetramine, propylenediamine, dipropylenetriamine, ethylene propylene triamine, ethylene dipropylene tetramine, diethylene propylene tetramine, ethylene tripropylene pentamine, butylenediamine, pentylenediamine, hexamethylenediamine, tetraethylenepentamine, 1,2-propylenediamine, dibutylenetriamine, tributylenetetramine, tetrabutylenepentamine, dipentylenetriamine, tripentylenetetramine, tetrapentylenepentamine, and a mixture thereof. The functional amine reactant can be an alkylamine, alkyldiamine, alkenepolyamine, polyoxyalkylamine or diamine, alkanolamine (e.g., mono/di/tri ethanolamine) or a combination thereof. Additional functional amine reactants are described as aminopolymers in Organic Polymer Chemistry, 2nd ed., Chapman and Hall, 1988, pp. 341-357, and incorporated herein by reference.

In a preferred example, the coating composition and/or the coating layer includes a guanidyl dye fixative that includes a guanidyl-carbonyl condensate. More preferably, the composition includes a guanidyl dye fixative that is (consists of) a guanidyl-carbonyl condensate. The included guanidyl-carbonyl condensate, preferably, has a structure imparted by an alkaline-catalyzed condensation of the guanidyl and the carbonyl reactants, or an acid-catalyzed condensation of the guanidyl and the carbonyl reactants. In one instance for, for example, inkjet papers, the coating composition can include about 0.5 wt. % to about 50 wt. %, about 1 wt. % to about 25 wt. %, or about 2 wt. % to about 10 wt. % of the guanidyl dye fixative (dry basis, solids); in another instance the coating composition can include about 5 wt. %, 10 wt. %, 15 wt. %, 20 wt. %, 25 wt. %, 30 wt. %, 35 wt. %, 40 wt. %, 45 wt. %, or 50 wt. % of the guanidyl dye fixative (dry basis, total solids). In still another instance for, for example, gravure papers, the coating composition can include about 30 wt. % to about 60 wt. %, about 30 wt. % to about 55 wt. %, or about 40 wt. % to about 50 wt. % of the guanidyl dye fixative (of the polymer on a dry basis, total solids); in another instance the coating composition can include about 30 wt. %, 35 wt. %, 40 wt. %, 45 wt. %, 50 wt. %, 55 wt. %, or 60 wt. % of the guanidyl dye fixative total solids (dry basis).

In another example, the coating composition and/or the coating layer can further include a filler dispersant. Herein, the filler dispersant is, preferably, a polymeric material selected to help support/disperse the filler in a solution (i.e. the coating composition). Preferably, the filler dispersant interacts with (e.g., chemically, physicochemically, electrostatically) surfaces of the filler and reduces the separation (e.g., settling) of the filler from a solution. That is, the filler dispersant helps keep the coating composition homogeneous. Commonly, the filler dispersant is a charged polymer, preferably, an anionic polymer. More preferably, an admixture of the guanidyl dye fixative and the filler dispersant does not flocculate, precipitate, form flocculants, form precipitants, or otherwise affect the homogeneity and/or rheology of the coating composition.

Coating compositions for and/or the coating layers of inkjet papers can include dye fixatives that include group 2-13 cations. In one instance, the herein described composition is substantially free of Group 2-13 cations. In another instance, the herein described composition is free of dye fixative that includes a group 2-13 cation. In still another instance, the composition includes a dye fixative that is a mixture of the guanidyl dye fixative and a “cationic” dye fixative that includes group 2-13 cations. Preferably, in this instance, the ratio of the weight percentages of the guanidyl dye fixative to the cationic dye fixative is greater than 1:1 (i.e. more guanidyl dye fixative by weight). More preferably the ratio has a value greater than 2, 3, 4, 5, 6, 7, 8, 9, or 10.

In another embodiment, the coating composition is employed to form a coated paper, for example, for use in inkjet printing. In one instance, the process of making the coated paper includes applying the coating composition, which includes a guanidyl dye fixative, to paper. The above described coating composition can be applied to the paper by, for example, spray coating, gravure coating, reverse gravure coating, rod coating, size press coating, blade coating, or curtain coating. In some instances where excess coating composition is applied to the paper, the excess can be removed by, for example, a blade or rod.

Examples of coating units suitable for obtaining uniform coatings on substrates include impregnation units, knife coating units, wire wound coating bars, roll coaters, spray coaters, size presses, nip presses, and the like. As one non-limiting example, paper can be treated with a coating composition by utilizing coaters, e.g., brush and air knife coaters, on-machine coaters, high speed blade coaters, light weight on-machine coaters, Gate roll coaters, double blade coaters, and those coaters presented in Fukui Terunobu, “A Review of Paper Coating. Paper Coating Technologies in the 20th Century”, Japan TAPPI Journal, 2001, 55, 1651-1667 and Jerzy Wypych, Polymer Modified Textile Materials (John Wiley & Sons 1988), both of which incorporated herein by reference.

The preparation of the coated paper can further include drying the coating composition carried on the paper to provide a coating layer carried on the paper (i.e., coated paper). In one instance, the coated paper can include the paper (e.g., paper substrate) and the coating layer (dry), where the coating layer includes about 5 wt. % to about 100 wt. %, about 10 wt. % to about 95 wt. %, about 25 wt. % to about 90 wt. %, about 40 wt. % to about 90 wt. %, or about 50 wt. % to about 99 wt. % of the guanidyl dye fixative (on a dry basis). As described herein, the coating layer is carried by the paper substrate, functionally, this means that the coating layer is carried on a surface of the paper substrate, preferably, without fully penetrating or equilibrating with the paper matrix. Preferably, the coating layer is carried by the paper matrix; more preferably, filling surface voids on one surface of the paper but not penetrating the paper; and even more preferably, not individually coating the paper fibers.

The drying of the coated paper after treating with the coating composition can include the application of heat, the application of vacuum, the application of both heat and vacuum, or the air drying of the substrate. Applicable methods for any particular substrate are known to those of ordinary skill in the art. As used herein, dry and drying mean that water or other solvents were removed from the substrate to the point that reapplication of water or other solvent would darken or visibly wet the substrate. Preferably, dry or drying is to less than about 10% by wt. to about 20% by weight water or other solvent, but may be 0% to about 20% by weight.

Preferably, the coated paper, for inkjet printing, described herein has an increased ink density relative to the same paper uncoated. For example, paper including the herein described coating layer, preferably, has an ink density that is at least about 2.5%, 5%, 10%, 20%, 25%, 30%, 40%, or 50% greater than an uncoated paper. In one instance, the black ink density on the herein described coated paper is at least about 2%, 5%, 10%, 15%, 20%, or 25% greater than the same paper uncoated.

Examples

Coated sheets (inkjet papers) were prepared by applying a coating composition to a 92 bright, 20 lb (75 g/m²), 30% recycled paper sheet. Drawing down the coating composition using a #0 rod. Drying the sheet in an industrial drier at a setting of 4.5 and then in a speedy drier at 105° C. for 2 minutes.

Prints were made using an EPSON Workforce WF-2630 printer using “pigment” based inks #220; and an HP Envy 5530 using dye based inks #61. Absolute ink density was measured using a densitometer, X-Rite 428.

Tables 1-4 show ink density results between different coating compositions and different inks. Coating compositions included the guanidyl dye fixative, the guanidyl dye fixative with a starch binder, and the guanidyl dye fixative with a latex binder.

TABLE 1 EPSON inks; Cationic guanidyl dye fixative Coating Composition (wt. %) Ink Density Ex. # GDF SB GCC Black Cyan Magenta Yellow 1 0 0 0 1.39 1.04 0.87 0.78 2 5 0 0 1.47 1.10 0.94 0.85 3 10 0 0 1.48 1.11 0.95 0.86 4 15 0 0 1.49 1.07 0.97 0.86 5 0 4 0 1.42 1.00 0.87 0.75 6 5 4 0 1.48 1.10 0.94 0.87 7 10 4 0 1.47 1.10 0.93 0.86 8 15 4 0 1.47 1.07 0.95 0.86 9 0 0 30 1.45 1.05 0.85 0.78 10 5 0 30 1.52 1.19 0.97 0.89 11 10 0 30 1.52 1.19 1.00 0.91 12 15 0 30 1.47 1.09 1.00 0.89 GDF = guanidyl dye fixative; SB = ethylated starch binder; GCC = Ground calcium carbonate.

TABLE 2 HP inks; Cationic guanidyl dye fixative Coating Composition (wt. %) Ink Density Ex. # GDF SB GCC Black Cyan Magenta Yellow 13 0 0 0 1.33 1.02 1.04 0.73 14 5 0 0 1.55 1.03 1.07 0.79 15 10 0 0 1.61 1.04 1.05 0.79 16 15 0 0 1.63 1.04 1.05 0.79 17 0 4 0 1.27 1.03 1.08 0.78 18 5 4 0 1.58 1.05 1.10 0.81 19 10 4 0 1.64 1.06 1.08 0.81 20 15 4 0 1.66 1.07 1.06 0.81 21 0 0 30 1.24 0.84 0.81 0.59 22 5 0 30 1.53 0.92 0.89 0.68 23 10 0 30 1.62 1.01 0.88 0.69 24 15 0 30 1.63 1.11 0.98 0.79 GDF = guanidyl dye fixative; SB = ethylated starch binder; GCC = Ground calcium carbonate.

TABLE 3 EPSON inks; Amphoteric guanidyl dye fixative Coating Composition (wt. %) Ink Density Ex. # GDF GCC LB Black Cyan Magenta Yellow 25 0 30 7 1.45 1.05 0.85 0.78 26 5 30 7 1.34 1.12 0.90 0.81 27 10 30 7 1.39 1.14 0.91 0.83 28 15 30 7 1.47 1.20 0.98 0.88 GDF = guanidyl dye fixative; GCC = Ground calcium carbonate; LB = latex binder (approximately 50% active).

TABLE 4 HP inks; Amphoteric guanidyl dye fixative Coating Composition (wt. %) Ink Density Ex. # GDF GCC LB Black Cyan Magenta Yellow 29 0 30 7 1.24 0.84 0.81 0.59 20 5 30 7 1.36 0.94 0.85 0.59 31 10 30 7 1.30 0.96 0.88 0.63 32 15 30 7 1.46 0.86 0.86 0.63 GDF = guanidyl dye fixative; GCC = Ground calcium carbonate; LB = latex binder (approximately 50% active).

The foregoing description is given for clearness of understanding only, and no unnecessary limitations should be understood therefrom, as modifications within the scope of the invention may be apparent to those having ordinary skill in the art. 

What is claimed:
 1. A coating composition for paper, the composition comprising: a binder and/or a filler; and a guanidyl dye fixative.
 2. The coating composition of claim 1, wherein the composition includes about 50% of the guanidyl dye fixative (dry basis, total solids), about 10 wt. % of a starch binder, and about 2 wt. % of a surfactant.
 3. A coated paper comprising: a paper substrate, and a coating layer carried by the paper substrate that comprises a guanidyl dye fixative.
 4. The coated paper of claim 3, wherein the guanidyl dye fixative comprises a guanidyl copolymer that comprises a reaction product of a guanidyl reactant and a carbonyl reactant, the carbonyl reactant selected from the group consisting of an aldehyde, a ketone, a urea, an amide, and a mixture thereof; and the guanidyl reactant selected from the group consisting of guanidine, 2-cyanoguanidine, guanidine salt, cyanamide, dicyanamide, biguanide, guanylurea, guanylthiourea, polycyclic guanidine, N-(4-aminobutyl)guanidine, 2-amino-5-guanidinopentanoic acid, imidodicarbonimidic diamide, (N-butylimidocarbonimidic diamide), (2-(methylguanidino) ethanoic acid), (2-[carbamimidoyl(methyl)amino]ethyl dihydrogen phosphate), cyanoguanidine, (2-guanidinoacetic acid), (3-(diaminomethylideneamino)propanoic acid), (N,N-dimethylimidodicarbonimidic diamide), (1-nitroguanidine), (4-amino-N-[amino(imino)methyl]benzenesulfonamide), (2-[10-(diaminomethylideneamino)decyl]guanidine dihydrochloride), melamine, alkyl guanidine, aryl guanidine, alkylaryl guanidine, alkyl biguanide, aryl biguanide, alkylaryl biguanide, and a mixture thereof.
 5. The coated paper of claim 3, wherein the guanidyl dye fixative comprises a guanidyl-carbonyl condensate.
 6. The coated paper of claim 5, wherein the guanidyl-carbonyl condensate is an alkaline-catalyzed guanidyl copolymer.
 7. The coated paper of claim 5, wherein the guanidyl-carbonyl condensate is an acid-catalyzed guanidyl copolymer.
 8. The coated paper of claim 3, wherein the coating layer comprises about 5 wt. % to about 100 wt. % of the guanidyl dye fixative (dry basis, total solids).
 9. The coated paper of claim 3, wherein the coating layer includes a binder and/or a filler.
 10. The coated paper of claim 9, wherein the filler is selected from the group consisting of calcium carbonate, kaolinite, a silicate, an aluminate, an aluminosilicate, a titanate, and a mixture thereof.
 11. The coated paper of any one of claim 10, wherein the coating layer comprises about 40 wt. % to about 70 wt. % of the filler.
 12. The coated paper of claim 9, wherein the binder is selected from the group consisting of a styrene butadiene copolymer, a styrene acrylate copolymer, an acrylic/vinyl acetate polymer, a starch, a polyvinyl alcohol, a polyvinylacetate, a latex, an acrylic polymer, an acrylic copolymer, a styrene-acrylate copolymer, a polyethylene-polyvinyl acetate, a polyethylene-polyvinylalcohol, sodium alginate, and a mixture thereof.
 13. The coated paper of claim 9, wherein the coating layer comprises about 1 wt. % to about 50 wt. % of the binder.
 14. A process of forming a coated paper comprising: applying a coating composition, that includes a guanidyl dye fixative, to paper; and then drying the coating composition on the paper to provide a coating layer carried by the paper.
 15. The process of claim 14, wherein the coating composition is applied by a method selected from spray coating, gravure coating, reverse gravure coating, rod coating, size press coating, blade coating, or curtain coating.
 16. The process of claim 15, further comprising removing excess coating composition from the paper by blade or rod.
 17. The process of claim 14, wherein the guanidyl dye fixative comprises a guanidyl copolymer that comprises a reaction product of a guanidyl reactant and a carbonyl reactant, the carbonyl reactant selected from the group consisting of an aldehyde, a ketone, a urea, an amide, and a mixture thereof; and the guanidyl reactant selected from the group consisting of guanidine, 2-cyanoguanidine, guanidine salt, cyanamide, dicyanamide, biguanide, guanylurea, guanylthiourea, polycyclic guanidine, N-(4-aminobutyl)guanidine, 2-amino-5-guanidinopentanoic acid, imidodicarbonimidic diamide, (N-butylimidocarbonimidic diamide), (2-(methylguanidino) ethanoic acid), (2-[carbamimidoyl(methyl)amino]ethyl dihydrogen phosphate), cyanoguanidine, (2-guanidinoacetic acid), (3-(diaminomethylideneamino)propanoic acid), (N,N-dimethylimidodicarbonimidic diamide), (1-nitroguanidine), (4-amino-N-[amino(imino)methyl]benzenesulfonamide), (2-[10-(diaminomethylideneamino)decyl]guanidine dihydrochloride), melamine, alkyl guanidine, aryl guanidine, alkylaryl guanidine, alkyl biguanide, aryl biguanide, alkylaryl biguanide, and a mixture thereof.
 18. The process of claim 14, wherein the coating composition includes a filler; wherein the filler is selected from the group consisting of calcium carbonate, kaolinite, a silicate, an aluminate, an aluminosilicate, a titanate, and a mixture thereof; and wherein the coating composition comprises about 30 wt. % to about 70 wt. % of the filler.
 19. The process of claim 14, wherein the coating composition includes a binder; wherein the binder is selected from the group consisting of a styrene butadiene copolymer, a styrene acrylate copolymer, an acrylic/vinyl acetate polymer, a starch, a polyvinyl alcohol, a polyvinylacetate, a latex, an acrylic polymer, an acrylic copolymer, a styrene-acrylate copolymer, a polyethylene-polyvinyl acetate, a polyethylene-polyvinylalcohol, sodium alginate, and a mixture thereof; and wherein the coating composition comprises about 1 wt. % to about 50 wt. % of the binder. 